The present invention relates to a power supply structure for a multichip package, and more particularly to a power supply structure for a multichip package in which high-speed integrated circuits are to be mounted.
Multiple packaging is one of the techniques for increasing the signal transmission speed between integrated circuits. Multichip packaging means the mounting of a plurality of integrated circuits on a single substrate. Within a multichip package, a plurality of integrated circuits are packaged in high density. The shorter distances between the integrated circuits result in the faster signal transmission between the circuits.
However, a further increase in processing speed of integrated circuits requires further improvement in signal transmission speed. A technique for satisfying this requirement, disclosed in the U.S. Pat. No. 4,819,131, is intended for further improvement in the signal transmission speed between integrated circuits.
Referring to FIG. 8, a plurality of integrated circuit chips 2 are packaged over a multilayer substrate 1. The integrated circuit chips 2 and the multilayer substrate 1 constitute a multichip package. Referring to FIG. 10, the multi-layer substrate 1 is mounted on a mother board 20. The multi-layer substrate 1 and the mother board 20 are connected to each other by input/output pins and power supply pins. Referring to FIG. 9, the input/output pins and the power supply pins constitute coaxial pins 3. Inner conductors 8 of the coaxial pins 3 are the input/output pins, which convey signals. Outer conductors 9 surpress waveform distortion or crosstalk of these signals. The elimination of waveform distortion or crosstalk result in the reduction of the distances between the input/output pins, which in turn serves to shorten the distances between the integrated circuit chips 2. Shorter distances between the integrated circuit chips 2 result in a higher speed of signal transmission.
The above-described technique achieve higher signal transmission speed within a multichip package. However, no effective technique has as yet been developed to increase the speed of signals transmission between the inside and the outside of a multichip package.
Referring again to FIGS. 8 and 10, on the rear face of the mother board 20 is provided a connector, not shown, to which an external unit is connected. Signals between the integrated circuit chips 2 and the external unit pass the connector on the rear face of the mother board 20, the mother board 20, the coaxial pins 3 and the multilayer substrate 1. The route which the signals pass is called the transmission path. The transmission path includes two kinds of connectors, i.e. the connector on the rear face of the mother board 20 and the coaxial pins 3.
If the transmission path is shortened, the speed of signal transmission between the integrated circuits and the external unit can be increased, and the distortion of signals can be improved by reducing the number of connectors included in the transmission path, because mismatching of impedances within the connector is one of the causes of signal distortion. Improvement of signal distortion can further increase the speed of signal transmission.
The requirements can be simultaneously satisfied by dispensing with the mother board 20, which is rather thick on account of the presence of power layers within. Therefore, by eliminating this mother board 20, the transmission path can be considerably shortened, and the number of connectors can also be reduced by one.
The main roles of the mother board 20 are to supply power to and to hold the multichip package. Therefore, in order to dispense with the mother board 20, some power supply structure to replace it should be developed. The power supply structure should also serve the purpose of holding the multichip package.